220 CHAPTER XVII. 



Dr. G-RUBLER, writing to MAYER (see the Grundzuge, LEE und 

 MAYER, p. 215), says: "Aurum chloratum fuscum contains 

 about 53 per cent. Au, the flavum about 48 per cent. ; in 

 both of them there should be only water and hydrochloric 

 acid besides the gold, no sodium chloride. Pure Auronatrmm 

 chloratum contains 147 per cent, of sodium chloride, though 

 samples are found in commerce with much more." 



APATHY (Mitth. Zool 8 tat. Neapel, xii, 1897, p. 722) 

 formerly employed the aurum chloratum flavum, but now 

 prefers the fuscum. 



A. Pre-impregnation. 



362. The State of the Tissues to be impregnated. The once 

 classical rule, that for researches on nerve-endings the tissues 

 should be taken perfectly fresh, seems not to be valid for all 

 cases. For DKASCH (Sitzb. Akad. Wi&s. Wien, 1881, p. 171, 

 and 1881, p. 516; and Ahhand. math.-phys. Cl. K. Sach. 

 Ges. Wiss., xiv, No. 5, 1887 ; Zeit. wiss. Mik., iv, 1887, 

 p. 492) finds that better results are obtained with tissues that 

 have been allowed to lie after death for twelve, twenty-four, 

 or even forty-eight hours in a cool place. 



363. COHNHEIM'S Method (Virchow's Arch., Bd. xxxviii, pp. 346 

 349 ; Strieker s Handb., p. 1100). Fresh pieces of cornea (or other tissue) 

 are put into 0'5 per cent, solution of chloride of gold until thoroughly 

 yellow, and then exposed to the light in water acidulated with acetic 

 acid until the gold is thoroughly reduced, which happens in the course 

 of a few days at latest. They are then mounted in acidulated glycerin. 



Results very uncertain and anything but permanent. 



364. LOWJT'S Method (Sifzgsb<r. Akad. Wien, Bd. Ixxi, 

 1875, p. 1). The following directions are from FISCHER'S paper 

 on the corpuscles of Meissner (Arch. mik. Aval., xii, 1875, p. 

 366). 



Small pieces of fresh skin are put into dilute formic acid 

 (one volume of water to one of the acid of 1'12 sp. gr.), and 

 remain there until the epidermis peels off. They then are 

 put for fifteen minutes into gold chloride solution (1| per 

 cent, to 1 per cent.), then for twenty -four hours into dilute 

 formic acid (1 part of the acid to 18 of water), and then 

 for twenty-four hours into undiluted formic acid. (Both of 

 these stages are gone through in the dark). Sections are 



